routermessenger.java

jxta_src_2.41b jxta 2.41b 最新版源码 from www.jxta.org

/*
 *
 * $Id: RouterMessenger.java,v 1.34 2006/01/06 19:29:08 bondolo Exp $
 *
 * Copyright (c) 2001 Sun Microsystems, Inc.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *       Sun Microsystems, Inc. for Project JXTA."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Sun", "Sun Microsystems, Inc.", "JXTA" and "Project JXTA"
 *    must not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
 *    permission, please contact Project JXTA at http://www.jxta.org.
 *
 * 5. Products derived from this software may not be called "JXTA",
 *    nor may "JXTA" appear in their name, without prior written
 *    permission of Sun.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
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 * SUCH DAMAGE.
 *
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of Project JXTA.  For more
 * information on Project JXTA, please see
 * <http://www.jxta.org/>.
 *
 * This license is based on the BSD license adopted by the Apache Foundation.
 */

package net.jxta.impl.endpoint.router;


import java.io.IOException;
import java.lang.reflect.UndeclaredThrowableException;

import net.jxta.endpoint.EndpointAddress;
import net.jxta.endpoint.Message;
import net.jxta.impl.endpoint.BlockingMessenger;
import net.jxta.impl.endpoint.IllegalTransportLoopException;

import org.apache.log4j.Level;
import org.apache.log4j.Logger;


/**
 *  Messenger for destinations which are logical peers. This messenger is used 
 *  only at the origin of routes. Incoming messages that are being forwarded to
 *  another peer to not go through here.
 **/
class RouterMessenger extends BlockingMessenger {
    
    /**
     *  Log4J Logger
     **/
    private final static transient Logger LOG = Logger.getLogger(RouterMessenger.class.getName());

    /**
     *  The source address of messages sent on this messenger.
     **/
    private final EndpointAddress srcAddress;
    
    /**
     *  The router we are working for. Also who we make route queries to.
     **/
    private final EndpointRouter router;

    /**
     * Constructor for a RouterMessenger.
     *
     * @param srcAddress the peer which will be identified as the message sender.
     * @param dstAddress the peer which is the final destination of the message.
     * @param r the router which this messenger is servicing.
     * @param hint potential hint information that we passed
     * @throws IOException Thrown if the messenger cannot be constructed for this destination.
     */
    public RouterMessenger(EndpointAddress srcAddress, EndpointAddress dstAddress, EndpointRouter r, Object hint)
        throws IOException {

        // Make sure that we do not ask for self destruction.
        super(r.getEndpointService().getGroup().getPeerGroupID(), dstAddress, false);

        this.srcAddress = (EndpointAddress) srcAddress.clone();
        this.router = r;
        
        // Probably redundant. getGatewayAddress does it.
        EndpointAddress plainAddr = new EndpointAddress(dstAddress, null, null);
        
        // We aggressively look for a route upfront. If it fails, we must refuse to create the messenger.
        EndpointAddress gate = router.getGatewayAddress(plainAddr, true, hint);

        if (gate == null) {
            throw new IOException("Could not construct RouterMessenger, no route for " + plainAddr);
        }
    }
    
    /**
     *  {@inheritDoc}
     **/
    public EndpointAddress getLogicalDestinationImpl() {
        return getDestinationAddress();
    }

    /**
     *  {@inheritDoc}
     **/
    public void closeImpl() {// Nothing to do. The underlying connection is not affected.
        // The messenger will be marked closed by the state machine once completely down; that's it.
    }

    /**
     *  {@inheritDoc}
     **/
    public boolean isIdleImpl() {
        // We do not need self destruction.
        return false;
    }

    /**
     * {@inheritDoc}
     **/
    public boolean sendMessageBImpl(Message message, String service, String serviceParam)
        throws IOException {

        if (isClosed()) {
            IOException failure = new IOException("Messenger was closed, it cannot be used to send messages.");
            
            if (LOG.isEnabledFor(Level.WARN)) {
                LOG.warn(failure, failure);
            }
            
            throw failure;
        }

        EndpointAddress dest = getDestAddressToUse(service, serviceParam);

        // Loop trying to send message until we run out of routes.
        Throwable lastFailure = null;

        while (true) {

            EndpointAddress sendTo = null;

            try {
                sendTo = router.addressMessage(message, dest);
                if (null == sendTo) {
                    break;
                }

                if (LOG.isEnabledFor(Level.DEBUG)) {
                    LOG.debug("Sending " + message + " to " + sendTo);
                }

                router.sendOnLocalRoute(sendTo, message);
                
                // it worked ! done.
                return true;
            } catch (RuntimeException rte) {

                // Either the message is invalid, or there is
                // a transport loop and the upper layer should close.
                // Either way, we must not retry. The loop could be
                // unbounded.

                lastFailure = rte;
                break;

            } catch (Throwable theMatter) {

                if (sendTo == null) {
                    // This is bad: address message was not able to
                    // do anything. Stop the loop.
                    if (LOG.isEnabledFor(Level.DEBUG)) {
                        LOG.debug("unknown error while routing: ", theMatter);
                    }
                    break;
                }

                // Everything else is treated like a bad route.
                lastFailure = theMatter;
            }

            // Currently we have only one long route per destination.
            // If the first hop is broken, then that long route is broken
            // as well. We must dump it, under penalty of trying it over and over again.

            EndpointAddress destPeer = new EndpointAddress(getDestinationAddress(), null, null);

            router.removeRoute(destPeer);
            
            // reset the router message for the next attempt.
            message.removeMessageElement(message.getMessageElement(EndpointRouterMessage.MESSAGE_NS, EndpointRouterMessage.MESSAGE_NAME));
        }

        if (lastFailure == null) {
            lastFailure = new IOException("RouterMessenger - Could not find a route for : " + dest);
        }

        // Except if we hit an illegal transport loop, we've exhausted all
        // the options we had, or there was a RuntimeException.
        // In both cases we must close. In the latter case it is a
        // precaution: we're not 100% sure that the message is at fault;
        // it could be this messenger as well. For illegal transport loops
        // the invoking messenger should close, not this one.

        if (!(lastFailure instanceof IllegalTransportLoopException)) {
            // FIXME - [e-mail] 20040413: as for all the transports. This used to be how this messenger broke itself.  Now,
            // all it does is too pretend that someone called for a nice close...just before the exception we throw causes the
            // BlockingMessenger state machine to go into breackage mode. Ultimately transports should get a deeper retrofit.
            close();
        }

        // Kind of stupid. Have to convert the runtime exceptions so that we
        // can re-throw them.

        if (LOG.isEnabledFor(Level.DEBUG)) {
            LOG.debug("Messenger failed:", lastFailure);
        }

        if (lastFailure instanceof IOException) {
            throw (IOException) lastFailure;
        } else if (lastFailure instanceof RuntimeException) {
            throw (RuntimeException) lastFailure;
        } else if (lastFailure instanceof Error) {
            throw (Error) lastFailure;
        } else {
            throw new UndeclaredThrowableException(lastFailure);
        }
    }
}